You need to speak to the move deleter to do this his house is in fuchsia city its right next to the Pokemon center.
Their are 7 HM's available in Firered.
The short answer is no. There is no Dive, HM 08, in Pokemon FireRed.
Where did you hear that? There is no such HM as remover in any game.
you get the HM strength
HM 07 can be found in the Ice Cave on Island 4.
You cannot get it in Pokemon FireRed. It doesn't matter because it is not necessary in Pokemon FireRed.
icefall cave
At rt 2.
waterfall
pour water on your game
Inside icefall cave.
Either by using the HM Strength or by using the HM Rock Smash